Method of coating insulated wire or the like and apparatus therefor



- Dec. zo, 1932.

METHOD OF COA:1ING INSULATED WIR. OR THE LIKE AND APPARATUS THEREFORlfiled Feb. 16, 1932 3 Sheets-Sheet ,1

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Dec.20, 1932. v A. fr. CANDY, JR 1,891,501

I TED IRE OR THE LIK ND APPARATUS THEREFOR l Filed Feb. 16, 1932:sheets-sheet 2 Dec..20, 1932. A. T. CANDY, JR

METHOD OF COIATING INSULATED WIRE OR THE LIKE AND APPARATUS THEREFORFiled Feb. 1e. 1952 s sheets-sheet s v lALBERT T. CANDY, JR., OF OAXPARK, ILLINOIS, ASSIGNOR T CANDY & COMPANY,i

Patented Dec. 20, 1932 UNITED STATES PATE NT OFFICE INC., 0F CHICAGO,ILLINOIS, A CORPORATION 0F ILLINOIS kMII'JfI-IOD OF COATING INSULATEDWIRE OR THE LIKE AND APPARATUS THEREFOR Application led February 16,1932. Serial No.'593,370.

My invention relates to a method of coating insulated Wire or the likeand apparatus therefor. It relates also to a method of makinfr insulatedWire-especially in colors.

, ile certain features of my invention are applicable `to impregnationof a continuous strand-like material it is particularly concerned Withthe problem of coat-ing Where the material to be deposited is coated asa lm of larger coated diameter than the object being coated. Manyfeatures of my invention are applicable to continuous coating processesfor strand-like objects other than Wire, but I here illustrate itparticularly applied to insulated wire for electrical purposes. Asapplied to insulated Wire, my application is specifically concerned withcoating an insulated Wire, the fabric braid of which has previously beenimpregnated.

AIn insulated Wire, the fabric braid has customarily been impregnatedWith a Weather proofing material-frequently a Wax-like material such asparaffin or a'pitch such as asphaltum pitch-to protect the rubberinsulation beneath the braid. More recently stearin pitch, or some otherflame-retarding composition has been used either as the irnpregnation oras an auxiliary coating on the previously mentioned impregnation, to.check the tendency of the braidto sustain combustion and carry Hainealong the Wire in the event of fire; When the impregnation or resultingsurface has been pitch-like, the Wire has been given a final coating ofparaffin to restore the surface characteristics'of 'the wire which Awerefound desirable when the braid was treated only with a paraffin im-vpregnation. The'desirable characteristics of the paraffin or otherWax-like surface are its lubricating qualities, which enable the wire tobe drawn through circuitous conduits Without danger of abrasion, and agenerally non# sticky surface, which avoids danger of the convolutionsof wire, on a spool or coil sticking together in Warm Weather as wouldbe the case with a pitchy surface.

A paraffin coating on pitch has certain objections, even apart from thedifficulties of applying it properly, among them: the paraflin, Whilenormally transparent, has a tendencyto fiake off and also to form moreor less opaque regions Where it has beensubjected to incidental scrapingaction, with the result that the appearance is not uniform and to agreater or less extent any color beneath the coating is `dulled; the dieor Wiper through which the paraffin coated\wire is passed often actsunevenly leaving bared or even abraided regions on the braid; thecoating may be contaminated with the impregnation or other underlyingmaterial; the paraffin is inflammable and therefor-e. in any event avery objectionable feature, making it necessary to keep the paraffinfilm at a minimum of thickness; and, considering the ultimate diameterof the Wire as the working limit, Whatever thickness is taken up by theparaffin film is so much less thickness of fire-retarding material. Ithas also been proposed to impregnate the braid With paraffin or asubstitute Wax and to coat this Witha fiame-stop material such asstearin pitch, the theory being that the melted stearin pitch, beingapplied at a higher temperature than the melting point of the paraffin,Will melt the paraffin and some of it Will find its Way through thecoating of stearin pitch sufficiently to make the surface of the coatingnon-sticky Without destroying its fire-retarding quality. This also hasits objections: the difficulty of controlling the intermixture of theparaffin with the pitch; the inability to secure a uniform mixture ofthe paraffin throughout the coating, for the mincoating which woulddestroy the flame-re tarding quality of the coating at such regions,

and thereby cut down its total fire-retarding effectiveness; the braidis left, for the most part, wholly impregnated with the parain whichconstitutes virtually a candle the burning of which is checked only by avery thin film of fire-retarding material which itself has, for the mostpart, too great a paraffin content to be effective; andthe inabilitytoproduce colored wire without greatly increased cost.

One object of my invention is to provide and produce a wire whichovercomes these objections in parafiin-over-pitch and inpitchover-parafiin wires, but which will still give the desirednon-sticky, lubricated, slick finished surface while retaining arelatively fire-retarding character.

I achieve this solution to the problem by using van impregnation and acoating, the compositions of which in general are substantially the sameor at least wherein the impregnation is as non-sticky as the coating andthe coating is as flame-retarding as the impregnation. To this end, theimpregnation and coating compositions which I use preferably containboth stearin pitch, or a substitute, and paraffin, or a substitute,there being enough wax-like material to make the composition non-stickyand slippery and to impart'a slick finish and enough stearin pitch or asubstitute to make the composition nevertheless sufficientlyflame-retarding. Apart from the aspect of coloring the wire (which Ishall presently discuss), the advantages of using a coating compositionhaving substantially the formula or characteristics of the impregnation,as compared with a coating of parafiin or substitute wax-like material,include: the greater fiexibility of the coating; more fire repellentprotection gelimination of infiammable surface film; better binding ofthe coating to the impregnation; and rendering immaterial thepossibility of contamination between the coating and impregnation.

Referring now to the problem of code wire in the assortment of colorsrequired by the trade, where the impregnation composition includespitch-and stearin pitch is most frequently used to give aflame-retarding character to the wirethe color given the wire is black,or at least very dark. `pigments are too expensive to make it feasibleto add sufficient quantities to the impregnation composition. Hence ithas been proposed to paint the impregnated wire before adding thetransparent paraffin coating. This has numerous objections: the addedexpense of another process; the cost of the paint itself; the' cost ofthe additional apparatus necessary for the paint dipping; the dullingeffect of the paraffin, even though normally transparent, over a brightcolor; the increased tendency toward white fiaky superficial appearanceof the parafiin coating and its tendency to flake offdue to the poorbinding with the smooth surface of the paint; and, in some instances,crumbling of the paint itself.

Thus another object of my invention is the provision and production of awire which is colored, wherein these objections are avoided and wherethe additional expense of coloring the wire is minimized and the coloris made of lasting brightness without danger of streaking by superficialabrasion. To this end, I use, in so far as practicable, the same basecomposition or formula for the impregnation that I do for the coatingand I add the pigment to the coating only. This gives an ample thicknessof colored film, but as the amount of coating composition used perthousand feet of wire is considerably less than the amount ofimpregnation used per thousand feet, a. great saving in the'cost ofpigment is effected as compared with the coloring of both compositionsor the use of a colored impregnation omitting a coating. My composition,when used for a colored coating; has a natural opaqueness which lessensthe amount of pigment required.

My invention is also concerned with the method or technique of coating.The usual method o'f coating a wire has been to pass a considerablelength of the wire back and forth over sheaves through a sizable vatcontaining the melted coating material, pass the strand or wire througha die, wiper or similar device to remove the excess material and tocontrol the thickness of the coating, and then to dry it by air passingthe wire over sheaves for a distance of some thirty to seventy-fivefeet. Some of the objections to coating by dipping are: the wire remainsin the melted coating composition long enough to permit heat to beimparted to the impregnation to a point of injuring it; the coatingmaterial may be contaminated by the impregnation; the excess coatingmust be removed down to the desired diameter or thickness of film; thedie or other means of removing the excess coating may cut through thecoating and bare the impregnation; the resulting finish must be a dull,wiped surface whether or not that kind of a finish is desired; and,because the wires pass back and forth through the vat containing thecoating material, it is difficult to provide proper agitators to keepthe material uniform without interfering with the wire, and thereforethe composition as coated often varies due to the settling out ofsolids. v i

Another method of treating, somewhat different from the dipping process,has been to pass the strand through a vat or receptacle containing themelted coating material and then-instead of passing wire up through thesurface of the liquid and to the die or scraper-to pass the wiredirectly through a discharge die in the side wall of the vat orreceptacle. From the discharge die, the wire emerges directly lintocooling Water or .passes through a long reach-through cool air to asheave. Such methods have been used principally for im regnations. Ifused for coatings, they. wo ld be subject to numerous objectionszTo keepthe melted material from running out through the discharge bore as theWire is pulledthrough, the bore has to be l -small renough to compressor squeeze the imterial beyond.- the diameter of the braid. The

scouring actiofn also increases the tension necessary to draw cthe wirethrough thel d1e.

- These methods would not operate effectively fest fluidity. Since thiswould for coating even if the diameter of the bore of the discharge diewere greater than that `of the braid, for the following reason: The

hot impregnation material-whether applied simultaneously with,Orimmediately preceding,'the coating layer-would be absorbed in so greatan amount per foot of wire that the resulting temperatures at the outerregions of the wire at the braid would be too high to congeal thematerial being applied. The

die would berelatively colder. As a result the fluidity, through a crosssection of the bore of the die, would begreatest-not at the surface ofthe bore-but at a region radially inwardly of the surface of the bore.The rapidly moving wire and the stationary parts of the die would partat the re 'on of greatbe yat the surface of .the bore, but rather at thesurface of the braid, the material could not be applied to asubstantially greater diameter than the thickness of the braid, and inany event it would not be accurately controlled.`

Another objection to the use of these treat- ,ing processes for coatingrelates to the problem of cooling or setting the coated material. It isnecessary that the coated material set before it touches the sheave orother metal part. If the wire is to be cooled by air after it emergesfrom the die, a very large amount of floor space must be taken up withone straight reach of wire some thirty to seventyfive 'feet long beforeit comes to its first sheave'a In those methods where the wire emergesfrom the die directly into a bath of cooling water, the water furtherchills the discharge end of the die, building up a restrictive neckwithin the end of the bore of the die,v

due to its increased congealing action with the result, 4alreadyexplained, of scraping the material to be deposited down to the surfaceof. the braid. Another objection to these processes is that it isnecessary to have a coating material which melts at a lowertemperaturethan the impregnation material.

A further object of my invention. is an im- -proved method of coatingwhich eliminates theseobjections. More specifically the objects include:a uniform controlled thicknessl of coating film; less tension forpulling the wire through the apparatus; greater permissible speed;permitting the use of a coating material with the same or-higher meltingpoint than that of the impregnation; the use of a tempering bath ofwater without chilling the die with its consequent objec-V tions andbefore touching any metal parts such asa sheave ga slick flame finishfor the coated wire; less dribble from the die; practically no scrapingsto be returned for remelting; and adaptability'to oblique or verticalpositions for the traveling wire.

In the method by which I achieve these objects, I preferably pass awire, the braid of which has been previously impregnated and cooled, ashort distance through a melted body of the coating composition andthence discharge the wire through a bore of substantially the diameterdesired on the finished product, through a short intervening air gap,down through the surface of, and into the. body of, a tank of temperingwater where it passes over sheaves and on to the winding spool.n Thebore of the discharge die is kept ata temperature higher than themelting point of the coating material. No cooling water comes in contactwith the discharge end of the die. Hence its temperature throughout isin excess of the melting point of the coating material. The wire and itsimpregnation, being previously cooled, is of less temperature than themelting point of the coating material. Therefore it congeals a layer ofcoating materialA upon itself. The length of wire exposed at any onemoment to the melted coating material is too short and the speed atwhich the wire passes is too great, to permit. the, body of the wire andits impregnation to be heated to any appreciable extent by the momentarysubmersion in the melted coating composition. Therefore, as the wirepasses through the coating apparatus, the body of the wire and theimpregnation do not rise in temperature enough to relinquish, bymelting, the layer of coating material which has, deposited upon it, butcontinues to accumulate a. congealed layer of the material. Should thiscongealed layer be of greater diameter than the bore of the hot die',the layer is either scraped or melted down to the bore of the die andpasses through the die with the dividing or part-ing at the surface ofthe bore. Preferably, however, the various factors are so controlledthat by the time the wire enters the borewof the discharge die, thelayer ofcongealed material has not built up to the diameter of the bore,but leaves @a substantial film of liquid meltedr material therebetween,which film is preferably lessened toward the discharge end of the boreby the continued accumulation or increase of the layer of congealedmaterial. The melted material immediately adjacent the surface makes aneffective lubricant for the easy and rapid passage of the wire.

For commercial code wire the diameter of the bore of the die may be .012inches greater than the diameter of the impregnated braid as it entersthe apparatus. This provides a coating film of approximately .006 inchesthick. As the wire emerges from the vdischarge end of the bore thegreater portion of the thickness of the coating is in congealed form.The remaining portion is so thin a film that it also congeals so quicklythat there is no opportunity for it to accumulate eccentrically of thewire or to drop from the wire.

Another object of my invention is apparatus for carrying out my methodwith its attendant advantages.

The foregoing with further objects, features and advantages of myinvention are set forth in the following description of a speciicpreferred embodiment thereof reference being made to the accompanyingdrawings wherein Fig. 1 is a side elevation of the coating apparatus ofmy invention with its associated supply reel, tempering tank and windingreel;

Fig. 2 is a plan view thereof;

Fig. 3 is a detail view of a portion of the apparatus shown in Fig. 1but on an enlarged scale, the coating material reservoir being brokeninto longitudinal vertical section;

F ig.\4 is a longitudinal vertical section of the applicator itself;

Fig. 5 is a transverse section taken on the line 5-5 of Fig. 3 throughthe applicator and showing the control valve;

Fig. 6 is a detail elevation of the valve taken on the line 6 6 of Fig.5;

F ig. is more or less a diagrammatic longitudi a section through thebore 266 of the disch ge die 26 and upon a greatly enlarged scale; and

Fig. 8 is a side elevation of a portion of the finished wire productwith the several layers progressively removed.

The apparatus shown in Fig. 1 comprises a supply reel of wire 10 to becoated, the reel 11 being mounted to unwind as it rotates against theretarding influence of the usual friction brake 12, which may be aweighted rope wrapped one or two turns about the shaft of the reel. Fromthe reel the' wire 10 is led over a sheave 13 mounted on a suitableframe 14 and through the applicator 15 down into a tempering tank 16,entering the body of tempering water 17 obliquely through its surface,thence over sheaves 18 and 19 within the vat, over a final sheave 2Oland to the winding reel 21 which is driven by a pulley 22 and belt 23from a convenient source of power. The applicator 15, referring to Fig.4, comprises a body, which may be of steel, penetrated by a longitudinalhole 24.

One end of the hole 24 is closely fitted or plugged by a cylindricalanterior die 25 and the other end by a posterior or discharge die 26preferably somewhat longer than the anterior die. A cylindrical chamber27 is left between the two dies. 4As shown in the transverse sectionofFig. 5 the applicator body may be split on a plane along the axis ofthe dies leaving lower and upper body members 28 and 28 held together bycap screws 29 and alined by suitable dowels. The purpose in halving thebody is to facilitate cleaning and the removal or substitution of thedies.

The dies have alined central bores 256 and 266 respectively. Thediameter of the discharge bore 266 is substantially that of the desiredover-all diameter of the coated wire. The anterior bore 256 isconveniently and preferably of the same diameter as the bore 266,although it may be some diameter intermediate that of the bore 266 andthe diameter of the entering wire. The applicator is mounted obliquelyon the frame 14 in such position that the center line of the borescoincides with the center line of the straight region of wiredeterminedy by the sheave 13 and the water vat sheave 18.

As shown in Fig. 5 there is a communication between the chamber 27 ofthe applicator and the bottom of hopper-like reservoir 30 by means ofthepipe connections 31 and 32 and a cut-oft valve 33. As here shown thereservoir 30 is square in cross section, the lower part being ofinverted truncated pyramidical form.- The reservoir 30 is divided intoan inner chamber 30a' and an outer chamber 300 by a partition 34 ofperforated sheet metal. The partition 34 is of square perimeter with itslower edges contacting the sloping sides of the hopper portion of thereservoir 30 and the upper edges extending to the top of the reservoir.'The reservoir is heated to keep the coating material well above itsmelting point by any suitable heating means such as a steam jacket, or,as here shown, electric heating elements 35 mounted on the exteriors ofthe sloping sides of the reservoir.

The coating composition, or its ingredients, are from time to time putinto the outer chamber 300 through the top of the reservoir in solid orpowdered form. The partition 34 acts as a screen to prevent the passageof the composition into the inner chamber until the composition has beenmelted and lumps eliminated. I prefer to employ an agitator 36. It :naybe carried by a shaft 37 depending from a bevel gear box 38 at the topof the reservoir, the agitator shaft being driven by a motor 39.

When there is no wire in the applicator 15 the melted composition wouldrun out through the bores 256 and 266. To avoid this I provide anautomatic control for the valve to shut it off when the wire has runout. This control preferably is a sheave 40 riding on the wire 10 andcarried at one end of a lever 41 which is pivoted at 42 on a bracketfrom the frame 14. The other end of the lever 41 is pivotally connectedto the sl-otted end 43 of a link 44 connected to the end of the valvelever 45. The slot 43 in the link 44, as shown in dotted lines in F ig.1, permits a certain up and down movement of the rider sheave 40 tocompensate for the dierent elevations of the wire 10 between the fulland empty positions of the supply reel 11, without actuating the valve.However when the wire runs o the supply reel l1, the rider lever 41drops down to a vertical position and pulls-the valve lever 45 over toclosed position. This immediately cuts oif further supply of coatingcomposition to the applicator chamber 27 and leaves but a relativelysmall amount to runout of the bores of the dies. This slight loss may becaught by drip pans not shown. In threading wire from a new Y supplyreel, the rider sheave'is not lifted up to position on the Wire untilthe threading has been completed and the wire is ready to be pulledthrough the applicator.

The body of the applicator and the dies are maintained at a temperatureWell above the melting point of the coating composition by electriccartridge unit heaters 46 inserted in holes drilled transversely throughthe body. As shown in Fig. 4 these heat units are disposed close to thedies. The dies fit, .the opening 24 in the body snugly so there is agood heat transfer from the body to them. One pair of cartridges isdisposed npposite the anterior die 25, one opposite the chamber 27 tokeep the contents hot and two pairs are disposed opposite the dischargedie 26. It is particularly advisable in my method to .keep the surfaceof the discharge bore 266 hot enough throughout its length to melt thecoating composition.v

In the embodiment lof my invention here disclosed, the wire supplied tothe applicator by the supply reel 11 consists (see Fig. 8) of the usualcopper conductor 50, layer of rubber insulation 51, fabric braid 52 andimpregnation 53. Many features of my invention are not particularlylimited to the composition of the impregnation. Among other impregnationmaterials which may be used, is the usual stearin pitch with little orno other ingredients added. My coating need not be applied directly overthe impregnation, For exan'iple, `as previously mentioned, a Waterproofingr impregnation of asphalt and pitch is sometimes used with acoating of stearin pitch over it. Many features of my invention areapplicable to the application of the final coating over thisintermediate coating of stearin pitch. However one feature of myinvention is concerned with the composition used as the impregnation.The material with which the wire may have been impregnated before beingpassed throu h the coating apparatus of my invention may e 35% stearinpitch, 15% of paraffin, 10% of other waxes, 15% of natural or syntheticresin and 25% of filler. This composition contains sufficient paraiiinor other wax-like material to render the surface of the impregnationnon-sticky and to afford a sufficient lubrication to permit its beingdrawn through conduits without danger of abrasion,without losing itsrelatively llame-retarding quality. As here shown the wire is fed to thecoating apparatus from a reel of wire which has previously beenimpregnated and of course cooled to room temperature. Should wire be fedto my coating apparatus directly from the impregnating apparatus, thewire should, for the fullest advantages of my apparatus and method, beproperly cooled for reasons heretofore and later explained. I

The coating composition employed is preferably of the same composition,except for the addition of pigmentif the wire is to be colored. Forcertain colors, the filler of the composition may be replaced bypigments of such bulk that they themselves form fillers.

My coating method and the operation of my apparatus is as follows: Apreviously impregnated and cooled wire 10 is unwound from the supplyreel 11, passed over the sheave 13, through the alined bores 256 and 266of the dies of the applicator 15, through the Water tank 16, around thesheaves 18 and 19, over the sheave 20 and to the winding reel 21. Thenthe rider sheave 40 is lifted on to the wire 10. This opens the valve 33and permits the melted wax to run down into the chamber 27 of theapplicator. The bore 256 being somewhat larger than the wire 10,`air isdisplaced through the bore 256 by the melted coating compositionentering the chamber 27 until the level of the liquid seals off thelower edge of the bore 256. The head of liquid composition in thereservoir 30 compresses the trapped air to raise the liquid level to aslightly higher level.' I have not found it necessary to provide a ventfrom the top of the chamber 27 to the height of the liquid level in thereservoir 30to remove the trapped air.

The winding reel 21 is then set in operation pulling the wire rapidlythrough the applicator 15. Once the wire is in motion, there is noleakage of coating composition 'through the anterior bore 256, despitethe clearance between the bore and the incoming wire. This is becausethe wire, being cold immedi- -ately starts to `congeal some of themelted composition on to its surface, thereby restricting the amount ofclearance. The factor of surface friction between the melted compositionand the congealed composition in so small an annular region, togetherwith the speed of the incoming wire, preclude the melted compositionflowing back all of the wagthrough the length of the bore 25o.

nless some means be provided for maintainin a constant speed (theexpense of whioh have not found necessary), the speed of the wire willvary because of the increasingxdiameter of the coil as the wire iswound. I d however that the speed used in wire treating practice issatisfactory, ranging from two hundred to three hundred feet per minuteat the start, and four hundred to five p hundred feet per minute at theend, of the conventional five thousand foot run, with my method, thisspeed may also be substantially increased.

The melting point of the composition described will range between 150and 180o F.

The reservoir is preferably maintained at a temperature of about 250o F.and the applicator at about 300 F.

The incoming wire being relatively coolat room temperature-a layer ofthe melted coating composition will, as previously described, becongealedupon the surface of the wire as it passes through the chamber'27. In Fig. 8 this congealed layer is illustrated somewhatdiagrammatically. The wire passes through the relatively short chamber27 so quickly that the congealed layer, I believe, continues toaccumulate throughout the ylength of the discharge bore 26?). The wireis not in the chamber 27 or in contact with the melted composition longenough for the cold wire to be heated even at its surface to anyappreciable extent. Consequently the congealing process continuesthroughout the passage of any given section of the wire through theapplicator. The entire coating, it will be borne in mind, is only a fewthousandths of an inch thick, the thickness in the diagram of Fig. 8being exaggerated for clarity.

Because the die is kept hotter, even at the surface of the dischargebore 265, than the melting point of the coating composition, a freefluidity of the composition will be insured at the surface of the bore,despite the congealing action. This prevents the layer of congealedcoating material building up to the full diameter of the bore while thewirel is in the bore. No deposit can build up on the surface of the boretending to restrict its effective size. By maintaining an outer reion ofmelted fluid coating compound throughout the length of the dischargebore 2612, the wire is insur-ed an excellent lubrication in its passagethrough the bore, with the result that greater speed can be obtained andless tension is required on the wire.

As suggested by the diagram of Fig. 8, the various factors-thetemperature of the incoming wire, the temperature of the melted coatingcomposition in the chamber 27, the temperature of the die 26, theconsistency of the coating material, the speed of the wire, the lengthof the die 26, etc.-are so controlled that, by the time a given sectionof wire reaches the discharge end of the bore 26h, the layer ofcongealed coating material has built up to such a diameter as to leaveonly a minimum clearance from the surfaces of the bore 26b for the outerfilm of fluid material. Thus as the wire emerges from the discharge endof the bore 266 it comprises the core of impregnated wire, a coating ofcongealed material and a surface film of liquid melted material. Thesurface film is preferably of considerabl lesser thickness than thecoating of congea ed material. The emerging film of melted material isso thin and evenly distributed that in the short interval of timeavailable the force of gravity does not have an opportunity toconcentrate the melted material on the underside of the wire to anyappreciable extent. The emerging fihn `of melted coating congeals beforesuch aberration can take place toany appreciable extent. The rapidcongealing of the emerging liquid film is due to three factors: First,the continued absorption of heat by the relatively cool body of thewire, second, the chilling effect of the air about the emerging liquidfilm and third, the slightly subsequent immersion in the tempered waterbath 17.

By inclining the direction of travel of the wire through the applicator,the wire may continue on down through the surface of the water andthrough the body of the water so that before it reaches the sheave 18the coating is tempered and set. By that time the contact with thesheave will not destroy theI slick flame finish given the wire. It isimportant to a proper finish of the wire that the coating be set beforecontacting a sheave or other part. This has resented a serious problemin the past, which has often been met by running the coated wire from adischarge die through a long air space before it touches a sheave orother part. This has required a considerable amount of factory space. Ithas also involved a long length of wire in the coating apparatus as awhole at any given instant. The length of wire required to thread a newreel of Wire in the coating apparatus is generally of an unworkmanlikeappearance both at the beginning and the end of the run of a reel ofwire. One feature of my invention isthat this threading length, whichmay be imperfeet. is greatly reduced.

If desired, the wire may be polished by the usual leather or rope wiper56 after the initial immersion in the water. 'Preferably, as shown inFig. 1, this is arranged between the sheaves 18 and 19, so that the wireis immersed again following the wiping. In the case of materials such asI have disclosed which have higher melting points than paraffin andtherefore do not lend themselves so readily to friction wiping at highspeed, a hot die may be substituted.

The inclination of the wire a's it passes through the applicator may beincreased or decreased as desired-even being increases to the vertical.As it approaches the vertical, the anterior die becomes unnecessary ifthe chamber 27 is placed at such a height or made of such a length thatthe head of melted material in the reservoir 30 does not cause themelted material tooverflow the chamber.

The ultimate over-all diameter of the coating is substantially, but notwholly, determined by the diameter of the discharge bore.

Within the length of the discharge bore there is a certain frictionallag between the film of melted material and the walls of the bore. Thistends to hold back some` of the liquid film, with the result'that theliquid film, when it emerged from the end of. the discharge bore, wouldbe a trifle less than the diameter of the bore. This tendency however islargelv offset by the pressure ofthe head of liquid composition in thereservoir which forces thel liquid film out against the frictional lag.

The'various pertinent factors-the pressure head, the speed at which thewire travels, the viscosity of the melted material and the thickness ofthe congealed coating in relation to the thickness of the liquid coatingat the discharge end of the bore-are preferably so balanced as toproduce a resulting over-all diameter of the coating the same as that ofthe bore.

F or different sizes of Wire, or for different thicknesses of coatings,anterior and posterior dies having bores of different sizes are readilysubstituted. Slight variations in the thickness of the coatings on agiven size of wire may be produced by varying whichever of thepreviously mentioned factors is most convenient.

While I prefer wherever feasible to use substantially the samecomposition (except for pigment) in the impregnation as in the'coating,it is expedient, when the coating is to be of certain colors` tosubstitute a coating composition where the active flame-reta'rdingingredient is something other than a very' dark .pitch such as stearinpitch. The expediency of this substitution isparticularly true of awhite Wire, and to some extent with blue and yellow wires if it isessential that the colors be bright. In such instances a base may besubstituted which has a characteristically light one hand, theadded costof the substitute as compared with the pitch-and-wax 'compositionpreviously described, vagainst, on .the other hand, the increased costof the relatively expensive blue, yellow or white pigments in thequantities which would be required satisfactorily to overcome theblackness of the pitch. Where substitutes are used for the coatingcomposition, waxes, resins or other ingredients may be added to controlthe viscosity and melting point preferably to the same melting point asthat of the impregnation.

I have previously mentioned that 4one of the advantages in treating thebraided Wire in two processes-an impregnation and a coating-even thoughthe impregnation composition and the coating composition be the sameexcept for pigment, is the saving in the cost of relatively expensivepigment. This however is not the only advantage. An important advantage,apart from the phaseof color, is this: If the impregnation and coatingwere combined into a lsingle operation, the relatively large mass of hotmelted material ab-Y sorbed by the braid would so raise the temperatureof the wire at the region of the braid as to preclude an effectivecongealing of the material toward the region of the ultimate diameter ofthe-finishedgtreated wire. This would tend to prevent bringing the layerof oongealed material sufficiently close to the surface of the dischargebore to secure the greatest benefits of my method whereby an accuratelycontrolled layer of material is deposited for a considerable thicknessbeyond the over-all diameter of the-braid.

In my coating method a relatively long discharge bore is advisable forthese reasons: The surface of a short bore would be chilled more rapidlythan the necessary heat could well`be applied to it; the long annularspace between the Wire and the die affords a more accurate metering ofthe material being coated; the long bore gives an advantageous ironingeffect; a long bore permits greater speed; if the bore were short, therewould be less region of frictional, lag of the melted film, with aresult that the head of liquid material could n'ot be so well balancedby the frictional lag, and hence the fluctuation in the liquid head bythe addition of the material to the reservoir from time to time wouldtoo readily vary the outfiow of melted material from the discharge bore;and, as the process of building up the layer ofA congealed materialcould not be carried forward to any appreciable extent Within 'thelength of a short bore, it would be difficult if not impossible so tocontrol the thickness of the layer of congealed material that by thetime it got to the short bore it would leave an intervening space of theproper thickness for the film of melted materialif vthis space wereinsufficient there would be a dalmning up at the entrance end of theshort bore which would block the flow of melted material, and if thespace were too great, the layer of melted material emerging from theshort discharge bore would be too thick to be congealed before it hadflowed to the underside of the wire to form a coating of eccentric crosssection and perhaps also to permit some of the liquid material to dropoff the wire.

Vhile I have described and illustrated this specific method, apparatusand article, I contemplate that many changes may be made therein withoutdeparting from the scope or spirit of my invention.

The apparatus, formula, method of making a wire, and the wire are thesubject mattcr of my application Serial No. 643,307 filed November 19,1932 which is a continuation in part of this application.

I claim:

l. The method of coating a wire which consists in first treating thewire to render its surface substantially non-absorbent, thencontinuously passingr a run of the wire, thus treated and at atemperature well below the melting point of the coating material,through a short distance in a body of the melted coating materialwherein the relatively cool surface of the wire causes coating materialto congeal as a layer thereon,.pass ing the wire with its congealedlayer through a discharge bore of considerable length, the diameter ofwhich is larger than the diameter of the wire to be coated bysubstantially twice the thickness of the desired coating, maintainingthe surface of the discharge bore at a temperature higher than themelting point of the coating material to preserve a surface film ofstill melted material, withdrawing the wire from the discharge borealong with the film of melted coating material surrounding the layer ofcongealed coating material, the film being so thin that it sets withoutsubstantial aberration, and passing the wire from the discharge borethrough an intervening air space and into a tempering liquid to set thecoating before it touches any wire guiding part.

2. The method of coating a wire which consists in first treating thewire to render its surface substantially non-absorbent, thencontinuously passing a run of the wire, thus treated and at atemperature well below the melting pointof the coating material, througha short distance in a body of the melted coating material wherein therelatively cool surface of the wire causes coating material to congealas a layer thereon, passing the wire with its congealed layer in adownward direction through a discharge bore of considerable length, thediameter of which is larger than the diameter of the wire to be coatedby substantially twice the thickness of the desired coating, maintainingthe surface of the discharge bore at a temperature higher than themelting point of the coating material to preserve a surface film ofstill melted material, withdrawing the wire from the discharge borealong with the film of melted coating material surrounding the layer ofcongealed coating material, the film being so thin that it sets withoutsubstantial aberration, and passing the wire in the same downwarddirection from the discharge bore through an intervening air space andthrough the surface of, and into, a tempering liquid to set the coatingbefore it touches any wire guiding part.

3. The continuous method of coating a strand-like article which consistsin passing the article through a body ofthe melted coating materialwherein the relatively cooler surface of the wire causes a layer ofcoating material to congeal thereon, passing the wire with its congealedlayer through a discharge bore of approximately the diameter of thedesired coating, maintaining the surface of the discharge bore at atemperature higher than the melting point of the coating material tomaintain a film of still liquid material about the layer of congealedmaterial, withdrawing the wire from the discharge bore, with a liquidfilm thereon, directly into exposure to air, and congealing the film.

4. The method of coating a wire which consists in continuously, rapidlypassing a' run of wire at relatively low temperature into a body ofmelted coating material to congeal a layer of the material on to thewire, passing the wire with its layer of congealed material through adischarge boreralong with an outer film of still melted material,maintaining the surfaces of the bore at a temperature above the meltingpoint of the material, maintaining a liquid pressure'on the film ofmelted material to counteract frictional lag 'thereon from the surfaceof the bore, and

withdrawing the wire from the discharge bore, along with the film ofmelted material surrounding the layer of congealed coating material,directly into exposure to air.

5. The method of coating a strand-like article which consists incontinuously, rapidly passing a run of the article at relatively lowertemperature 4into a melted body of the material to be coated, congealinga layer of the material on to the article, passing the article with itslayer of congealed material through an obliquely disposed discharge borealong with an outer film of still melted material, maintaining thesurface of the bore at a temperature above the melting point of thematerial, the liquid film in the obliquely dis, posed bore tending torun downwardly to counteract the frictional lag of the film against thesurface of the bore, withdrawing the article from thedischarge bore,along with the film of melted material surrounding the layer ofcongealed material, directly into exposure to air and thence continuing,

obliquely through the surface of, and into, a body of tempering liquid.

' 6. The continuous method of coating a strand-like article whichconsists inimmersing the article in the melted coating material,congealing a layer thereof on to the article, passing the article andits congealed layer through a discharge bore, maintaining a film ofstill melted coating material about the layer while passing through the.bore with the greatest fluidity at the surface of the bore, andcongealing the material of the film after it leaves the bore.

7. The continuous method of coating a strand-like article which consistsin immersing the article in the melted coating material and passing thearticle through a discharge bore of considerable length and ofapproximately the diameter of the desired coating, maintaining thesurface of the bore at a temperature above the melting point of thematerial, withdrawing the article from the bore with a ilm of stillmelted material thereon, and congealing the lilm after it leavesthebore.

8. The continuous method of coating a strand-like article which consistsin immersing the article in a melted body of the coating material to becoated and withdrawing the article from the body through a dischargebore, the surface of which is maintained at a temperature above themelting point' of the material, with a ilm of still melted coatingmaterial surrounding the article as it emerges from the bore.

strand-like article which consists in passing the article downwardlythrough a bore with melted coating material surrounding the article andbetween it and the bore to the dis charge end of the bore, the surfaceof the bore being maintained at a temperature above the melting point ofthe coating material, and counteracting the frictional lag of the meltedmaterial on the surface of the bore by maintaining the bore in radownwardly disposed direction.

1l. The continuous method of coating a strand-like article whichconsists in passing the article downwardly through a bore with meltedcoating material surrounding the article and between it and the bore tothe discharge end of the bore, the surface of the bore being maintainedat a temperature above the melting point of the coating material,

and counteracting the frictional lag of the

